Character strings are generally input into a computing device using a keyboard which provides one key for each character. For devices which have only little space available for a keyboard, such as telephones or navigation devices, it is known to combine a multitude of alphabetical letters using in each case one key, and to pick out the suitable letter by a corresponding selection after pressing this key. However, this method likewise requires a minimum number of keys available to a user. It is furthermore known to provide the user with a list from which he/she is able to select individual characters. In this case, for example, the list is formed such that only inputtable characters are selected. However, a user must go through a possibly long list of characters for each input to in each case reach the character he wants in the linearly displayed list.